Cow & Hindu mythology:
Kamadhenu, the sacred cow which grants all wishes and desires, is an integral part of Hindu mythology. This divine cow, which lives in swargalok (heaven), emerged from the ocean of milk (ksheerasagar) at the time of samudramanthan (the great churning of the ocean by the gods (suras) and gemons (asuras). It was presented to the seven sages by the Gods, and in course of time came into the possession of Sage Vasishta.
Kamadhenu's complexion is like the white clouds. Every part of cow's body has a religious significance. Its four legs symbolize the four Vedas, and its teats the four Purusharthas. Its horns symbolize the gods, its face the sun and the moon, its shoulders Agni (the god of fire), and its legs the Himalayas.
Kamadhenu is also well-known through its other five forms: Nanda, Sunanda, Surabhi, Susheela and Sumana.
Mythologically, Brahma (the creator) created the brahmins (priests) and the cow at the same time, the Brahmins were to recite the religious scriptures while the cow was to afford ghee (clarified butter) for offerings in religious sacrifices. Brahma also affirmed it to be the mother of gods, ought to be worshipped and anybody who killed a cow or allows another to kill it, was deemed to rot in hell, for as many years as there are hair upon his body.
The cow symbolizes the dharma itself. It is said to have stood steadily upon the earth with its four feet during the Satyug (world's first age of truth), upon three feet during the Tretayug (the second stage of less than perfection), upon two feet during the Dwaparyug (the third stage of dwindling and disappearing perfection) and only on one leg during Kaliyug (the fourth and current age of decadence).